This invention relates to a bread making apparatus and its temperature control method suitable for a heat cooking apparatus including oven ranges and the like.
FIG. 17 is a plan view which shows the structure of an operation panel surface of a bread baking apparatus disclosed in a Gazette, U.M. Laid Open No. Hei-1 (1989)-108232. In the Figures, 51 is a main body case, and 52 is an operation panel. This operation panel 52 has a menu switch 53 which selects the kind of bread such as regular bread, french bread and the like, pre-engaged switches 54, 55 which set the baking time for the bread, a reset switch for cancelling the initial setting of these baking times, a start switch 56 for initiating bread baking, an indicator 58 which indicates time and errors, and a control dial 59 for controlling the bread baking state. The numeral 60 is an indicator lamp arranged at an upper portion of the operation panel 52 and indicates the kind of bread selected by the menu switch 53 and the completion of each process.
FIG. 18 is a sectional view which shows the inner construction of the bread making apparatus. In FIG. 18, 61 is a support legs, 62 is an upper portion case, 63 is a lid which opens and closes freely, 64 is a stand frame, 65 is a bearing plate, 66 is an inner case, 67 is an oven heater, 68 is a bread baking case, 69, 70 are a couple of latching pieces and 71 is a stand plate.
Further, 72 is a bearing portion, 73 is a metal, 74 is an upper rotation axis, 75 is a stirring motor, 76 is a belt, 77, 78 are pulleys, 79 is an outlet axis of the stirring motor 75, 80 is a lower rotation axis, 81, 82 are clutch bodies and 83 is a stirring blade.
The numeral 84 is a glass window, 85 is a heat-reflecting plate, 86 is an air absorption guide, 87 is an air absorption hole, 88 is a air blow guide, 89 is a blower fan, 90 is a countercurrent preventive plate, 91 is a sensor for mixed bread ingredients, 92 is a heat insulator, 93 is an oven sensor fixed in an inner case 66, and 94 is a wind-blowing motor.
FIG. 19 is a circuit view which shows the structure of a control circuit of the bread making apparatus. In FIG. 19, the same or the corresponding portions as FIG. 17 and FIG. 18 are shown with the same marks. In FIG. 19, 101 is a transfer switch for exchanging the dough sensor with the oven sensor 93, 102 is an integrator, 103 is a comparator circuit, 104 is a thermostat, 105 is a voltage-watching circuit, 106 is an instantaneous watching timer and 107 is a microcomputer. This microcomputer 107 is composed of RAM and ROM, and also of I/O port and A/D convertor. The ROM stores a standard program and other necessary data for bread making.
The numeral 108 is a converter for inputting the heater current of the oven heater 67 into a microcomputer 107, 109 is a relay circuit for the on/off functions of the heater current of the oven heater 67, and 110 is a triac which controls the heater current of the oven heater 67. The numeral 111 is an amplification circuit, and 112 is a speaker which gives off an alarm. The numeral 113 is a relay circuit for controlling the blower motor which controls the on/off functions of the blower motor 94 and 114 is a relay circuit for the stirring motor control which controls the on/off functions of the stirring motor 75.
FIG. 20 is a timing chart which shows a sequence of action of the bread making apparatus.
This bread making apparatus can produce bread by putting the bread ingredients in the baking case 68, then sequentially kneading or stirring and fermenting by the sequence shown in FIG. 20, and baking. Further, when the bread is being produced, each time step in the timing chart shown in FIG. 20 is adapted to be changeable by using a menu switch and preengaged switches 54, 55 for setting the bread baking times from the outside, whereby bread suited to one's individual taste can be made.
In the conventional bread making apparatus, the set temperature during the bread baking step is initially set with no consideration for the temperature outside the apparatus. As a result, when bread is baked consecutively a number of times, the problem that arises is that the quality of the first bread baked is different from the second and third ones. This is because the temperature of the oven heater 67 during the baking step becomes altered according to the temperature of the bread making apparatus itself, the retained temperature inside the bread baking case 68, and the temperature of the room wherein the bread making apparatus is placed.
This invention is intended to remove such problems and its objective is to provide a bread making apparatus which can produce bread having stable quality not influenced by the number of times the apparatus is consecutively used, the temperature of the bread making apparatus itself, the retained temperature of the bread baking case 68, or the temperature of the room wherein the bread making apparatus is placed.
A temperature control method of the bread making apparatus according to the conventional technique will be described as follows.
Namely, as shown in FIG. 18, a baking oven which bakes the kneaded dough with water is used together with a kneading container having stirring blades 83 at the bottom thereof, and at the lower outer circumference of this baking oven, an oven heater 67 is arranged.
Temperature control of this baking oven is performed by detecting it indirectly with an oven sensor 93 of a thermistor or the like fixed at an outer wall of an accommodated case of the baking oven. The numeral 75 is a driving motor for kneading blades.
Temperature data detected by the oven sensor 93 is incorporated by the control device containing a microcomputer therein, said control device keeping the heater "on" until the incorporated temperature reaches a certain set temperature in order to obtain the desired inner object temperature T.sub.1 of the baking oven at the time of bread baking. When the temperature reaches the set temperature, the heater turns "off", and the inner temperature of the baking oven then continues to rise with a time lag by the remaining heat. Since the heater is already "off", the inner temperature of the baking oven begins to fall and when the temperature detected by sensor reaches the set temperature t.sub.0 again, the heater is turned "on". In other words the heater is set "on" or "off" by taking the set temperature t.sub.0 as a standard. The set temperature t.sub.0 is the temperature which brings the inner temperature of the baking oven to the desired temperature T.sub.1 (e.g., 150.degree.) and is in general set at a slightly higher temperature (e.g., 180.degree.).
The above illustrated control is shown in FIG. 22.
Namely, (a) in FIG. 22 shows a change in detected value of the oven sensor 93, (b) shows the water level of the temperature in the practical baking oven, and (c) shows the on/off switching time of the heater 67.
As is clear from (a) and (c) in FIG. 22, when the detected value of the oven sensor 93 after the heater 67 comes "on" reaches the set temperature T.sub.0 memorized in the control unit, the heater 67 is turned "off" by the control unit. Since the temperature in the case continues to rise for a while even with the heater off, the detected value of the oven sensor 93 also continues to rise for a while, and then comes down.
When the detected value of the oven sensor 93 reaches the set temperature t.sub.0 again by the continued descent of the temperature, the heater 67 turns "on" again and heating is initiated. Although the descent of the detected value of the oven sensor continues for a while, its value begins again to rise before long.
After this, the same control is performed. As described above, in the conventional temperature control, since the heater 67 turns on or off, respectively, when the detected value of the oven sensor 93 crosses the set value t.sub.0, the practical inner temperature results in considerable variation with respect to the objective value T.sub.1 by all means and is unstable as shown in FIG. 22(b).
This invention provides a novel control method which decreases the breadth of the temperature variation in the kitchen case to as low a variation as possible.